1. Field of the Invention
The present invention relates to a steering device for a vehicle which turns vehicle wheels according to operation of a steering member.
2. Related Art
A steering device for a vehicle which includes a first sun gear connected to a steering member, a second sun gear which is operated according to operation of the steering member and connected to a steering mechanism for turning vehicle wheels, a first planet gear having external teeth and meshed with the first sun gear, a second planet gear which is rotated integrally with the first planet gear and has external teeth meshed with the second sun gear, and a carrier for supporting the first and second planet gears so as to revolve and rotate on their own axes, the steering device being constructed in such a manner that at least one of the first and second sun gears is a profile shifted gear, whereby the numbers of teeth of the first and second sun gears are made different from each other, and the first and second planet gears are formed on a columnar body which has external teeth of the same number at both end parts thereof, whereby the number of components and working steps can be reduced has been known (Reference should be made to Japanese Patent Publication No. JP-A-2005-344757, for example).
However, in the steering device in JP-A-2005-344757 which is constructed in this manner, the two planet gears are arranged outside of the sun gears having the external teeth in a radial direction and at positions divided in two in a circumferential direction so as to revolve and rotate on their own axes. For this reason, an area including the planet gears becomes large-diameter in the radial direction, which makes the steering device large-sized. Moreover, lubricant to be applied to the teeth of the sun gears and the planet gears is likely to be scattered to the exterior, and sliding speed of the planet gears having the external teeth is so high that vibration noise in meshed parts becomes loud. Therefore, measures for overcoming such drawbacks have been desired.